Extrusion press for indirect extrusion

ABSTRACT

An extrusion press for indirect extrusion has a sealing plate at one end of the bore of the billet container. This sealing plate extends a certain distance into the bore where it provides a seal against the wall of the bore. The plate also has a recess for accommodating a dummy block during extrusion, and a piston is provided behind the sealing plate to push the dummy block and butt end out of the recess at the end of extrusion.

The invention relates to a sealing plate or plug for closing the end ofa billet container bore during indirect extrusion. The invention extendsto a sealing plate arrangement and to an extrusion press including suchan arrangement. The invention is suitable for use in the indirectextrusion of both light and heavy metals.

Indirect extrusion is carried out by forcing a billet containercontaining an extrusion billet over a die mounted on the end of a hollowstem. The extruded section leaves the press along the hollow stem. Theback end of the billet container bore is closed by a sealing plate, andat the end of the extrusion process, a butt end or extrusion discard isleft against this plate. The sealing plate must seal tightly in the boreto prevent the billet material from flowing out and provision must bemade for separating the butt end from the sealing plate after extrusion.

An indirect metal extrusion press is known (German Offenlegungsschrift2,202,151), in which the sealing plate is hollow at its front end andthe diameter of the hollow corresponds to the diameter of the containerbore. This hollow recess can contain part of the extruded billet as anextension of the container bore. The recess in the sealing plate howeveris filled completely with new extruded material during the firstextrusion operation, and in all further extrusions the sealing platerecess remains filled with old extruded material from the firstoperation. The object of this invention was to carry out an extrusionoperation without a butt end and thus without material loss, while stillpreventing the die and sealing plate from coming into contact at the endof the extrusion process. The disadvantage of this construction is thatwhen a new billet is slid into the container bore, oxide particles andscale collect in front of the butt end remaining in the sealing plate.These particles, in the case of extrusion without a butt end, flow intothe extruded section at the end of the extrusion process and impair theproduct quality. In extruding light and heavy metal, in particularbrass, funnel formation and piping occur in indirect extrusion processesat the end of extrusion. For this reason a butt end is necessary toobtain a satisfactory extruded product.

In this construction the sealing plate lies flat, hard up against theend of the container. Thus material to be extruded can flow radiallyoutwards between the abutting surfaces if these sealing surfaces aredamaged, or if the sealing pressure between the container and movingcross-head is too low or if metal residue sticks to the sealing surfacesafter the shearing operation. A further disadvantage is that the tightlyfitting sealing plate lies outside the heated billet container, so thatduring the extrusion process heat is extracted from the billet to beextruded. This leads to non-uniform product quality over the length ofthe extruded article.

A device for removing the extrusion residue in an indirect metalextrusion press is also known (German Pat. No. 1,452,291). Thiscomprises a shearing mandrel axially slidable in the sealing plate forseparating the extruded article from the butt end and for then pressingthe butt end out of the sealing plate. This is done by a shoulderdisposed on the shearing mandrel pressing against a pressure plate,which completely fills the front end recess in the sealing plate, afterthe extrusion has been cut by the shearing mandrel descending into thedie opening. The pressure plate then moves against the butt end still inthe sealing plate. The power for this pressing action is obtained from ahydraulically operated piston located on the axis of extrusion behindthe shearing mandrel.

A disadvantage of this is that this shearing operation can only becarried out in practice if a shearing mandrel adapted to the extrudedprofile is available. In single extrusion presses extruding profiles ofsimple cross-section this is attainable, but is limited by the fact thatwhen extruding a new profile, both the shearing mandrel and the guidepiece for the shearing mandrel must be changed.

According to the invention, there is provided a sealing plate forsealing one end of the bore of a billet container in an indirectextrusion press, the sealing plate having a cylindrical part, with acylindrical interior recess, adapted to fit tightly into the containerbore, the cylindrical recess being shaped so as to receive a dummyblock, and an aperture in the sealing plate through which a piston canact to eject the dummy block and butt end from the recess, whenrequired.

The invention also extends to an extrusion press for indirect extrusionwhich comprises a counter platen and a cylinder cross-head joined by tierods, a hollow stem mounted at one end on the counter platen andcarrying a die at its other end, a billet container, a moving cross-headmovable between the cylinder cross-head and the counter platen so as tomove the billet container over the hollow stem, and carrying a sealingplate having a hollow cylindrical part which fits tightly into the boreof the billet container for sealing one end thereof, the hollowcylindrical part forming a cylindrical interior recess for receiving adummy block, and a piston projecting through an aperture in the sealingplate and actuable to push the dummy block out of the recess.

In a further development of the invention, the dummy block to beinserted into the recess may be heated outside the press and slid beforethe respective extrusion operation into the recess in the sealing plate,and withdrawn from the recess by means of the piston together with thebutt end at the end of the extrusion process.

As a result of heating the dummy block before the extrusion operation,no heat will be extracted from the billet to be extruded. The extensionof the hollow cylindrical sealing plate into the bore of the billetcontainer means that, in addition to efficient sealing, the part of thesealing plate extending into the container is heated by the container.

The inner diameter of the sealing plate recess may be approximatelyequal to the bore diameter of the billet container. This construction isused advantageously in extruding heavy metal and separating with a sawbetween the butt end and die with the extruded section partly drawn backafter extrusion. With this method of centering, the die cannot besatisfactorily supported during shearing.

The thickness of the dummy block to be inserted into the recess in thesealing plate may be advantageously chosen in accordance with therequired butt end thickness. In this case the thickness of the butt enddepends upon the deformation ratio and billet diameter.

In indirect extrusion with cold or hot lubricated billets, the dummyblock may be connected to the piston and its thickness may fill thedepth of the recess in the sealing plate. In this way, lubricant may becompressed between the annular surface of the dummy block and the innerwall of the recess. The gap between the centering surfaces of thesealing plate and container bore is on the one hand made as small aspossible and the gap between the centering surfaces of the dummy blockand the bore of the sealing plate recess is on the other hand made aslarge as possible. During the extrusion process, lubricant previouslyplaced in the sealing plate recess is brought up to pressure and thehollow cylindrical part of the plate is so deformed in its elasticregion that an efficient seal is assured between the container bore andsealing plate.

The invention will be further described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a sectional view, on one side only of a press center line, ofa first embodiment of the invention at the end of the extrusion process,

FIG. 2 is a view of the FIG. 1 embodiment with the moving cross-head andbillet container retracted and the butt end projecting for shearing.

FIG. 3 is a sectional view corresponding to FIG. 1, of a secondembodiment of the invention,

FIG. 4 is a view of the FIG. 3 embodiment with the moving cross-head andbillet container retracted and the butt end projecting for shearing.

FIG. 5 is a view similar to FIGS. 1 and 3, showing a further embodimenthaving a special form of die inlet and dummy block, and

FIG. 6 is a sectional view taken along lines A--A of FIG. 5.

In an indirect metal extrusion press, which is not illustrated in detailbut which comprises a cylinder cross-head, counter platen and tie-rodsconnecting these latter, and a main operating ram sliding in thecylinder of the cylinder cross-head with a moving cross-head 1 fixed tothis ram. A sealing plate 3 is provided at the end of the movingcross-head facing the counter platen, and is centered by means of aclamping and centering ring 2. A cylinder 4 acting as a push-out deviceis disposed in the moving cross-head 1 on the extrusion axis behind thesealing plate 3, and a double-acting piston 7 is guided in this cylinderand is actuated by way of bores 5 and 6. Its piston rod is in the formof a plunger 8. The plunger 8 is guided in a bore 9 in the sealing plate3.

At the front end of the cylindrical sealing plate 3 facing the counterplaten, there is provided a cylindrical recess 10 into which the plunger8 acts. During the extrusion process the sealing plate 3 lies with ashoulder 11 against one end 12 of a billet container 13. A hollowcylindrical part 14 of the sealing plate is therefore accuratelycentered by its cylindrical annular surface 16 in the bore 15 of thebillet container 13, where it is a tight fit, during the extrusionprocess.

A tool support 17 is provided on the counter platen, not shown, and ahollow stem 18 is centrally fixed there, on a supporting pressure plate19. A die 20 is provided at the front end facing the sealing plate 3.The billet container 13, which is guided on press guides, not shown, andis axially slidable by means of hydraulically operated sliding pistonsand piston rods, not shown, receives a billet 21 in its bore before theextrusion process starts. To load the ingot 21, the moving cross-head 1with the sealing plate 3 is moved towards the right, and the billet 21is inserted into the bore 15.

A dummy block 22 is inserted, before the extrusion process starts, intothe recess 10 of the sealing plate 3. This block 22, against which thebutt end or extrusion discard 21' of the billet 21 rests, is heatedoutside the press before the extrusion process to avoid loss of heat dueto the billet having to heat the block up.

To carry out the extrusion process the moving cross-head 1 is firstmoved to the left together with the sealing plate 3, so that theshoulder 11 rests against the front end 12 of the billet container 13,and the billet is contained between the die 20 and the hollowcylindrical part 14 of the sealing plate.

At the beginning of the extrusion process a part of the billet 21 restsin the form of the future butt end 21' in the recess 10 against theheated dummy block 22. The extrusion 21" which forms during theextrusion process flows towards the left through the opening 23 in thedie 20 and the bore 24 of the stationary stem 18. The billet container13 is therefore made to slide by the moving cross-head together with thesealing plate, and thereby slides over the stationary stem 18 and thedie 20 disposed at its front end.

The butt end 21' formed at the end of the extrusion process is locatedpartly in the recess 10 in front of the dummy block 22, and partlybetween the front end of the die 20 and the front end of the hollowcylindrical part 14 of the sealing plate.

The billet container 13 is then moved completely towards the left untilit abuts the tool support 17 (see FIG. 2). As the moving cross-head 1with the sealing plate 3 travels back towards the right, the plunger 8is actuated to push the butt end 21' and the block 22 adhering thereto,out of the recess 10. The front end 12 of the billet container 13 andthe die 20 are now flush with each other. A shearing device 25 disposedon the billet container 13, or brought from outside the press, shearsthe butt end 21' from the extrusion 21" with its knife 26. This methodof separating the butt end from the extrusion is normally used inextruding light metal.

In FIG. 3, the inner diameter of the recess 10 of the sealing plate 3 isapproximately the same as the bore diameter 15 of the billet container13. In order to permit the hollow cylindrical part 14 of the sealingplate to take up its position in the bore of the billet container 13,this has a stepped portion 29 at one end for accepting the part 14.After the extrusion 21" has been extruded (see FIG. 4) and the billetcontainer 13 has travelled back towards the left end position, themoving cross-head 1 travels back to the right with the sealing plate.The dummy block 22, butt end 21' and extrusion 21" are moved togethertowards the right because of the friction between the surface of thebutt end 21' and the wall of the recess 10. A saw 27, either mounted onthe press or brought from outside, and driven by a motor 28, cuts offthe extrusion 21" from the butt end. This method is normally used in thecase of heavy metals. The extrusion 21" is then pushed through the die20 by the extrusion stump 21' " which forms part of the butt end 21', onthe moving cross-head 1 being moved towards the left. When extrudingheavy metal, a sealing plate having a recess 10 with inner diameter asshown in FIG. 1 may also be used. However, the larger recess ispreferred, because the friction between the butt end and the recess ishigher in this case and so the butt end 21' stays more securely in therecess.

The dummy block 22 shown here has a raised boss 22' on that side whichfaces the butt end 21'. This leads to a smaller loss of billet materialduring extrusion and also prevents material from the dead region of thebillet flowing into the extruded section and leading to the so-calledpiping defect.

In FIG. 5 the die 20 is provided with a special inlet cone 20'. Thebillet 21 is lubricated on all sides and the dummy block 22 is providedwith a front end surface corresponding to the inlet cone 20'. There is anarrow gap 30 between the billet container bore 15 and the cylindricalannular surface 16 of the sealing plate 3, and a larger gap 31 betweenthe bore of the recess 10 and the outer diameter of the dummy block 22.Grease, or other lubricating fluid used, can flow at the beginning ofextrusion through the larger gap 31 into the recess, and elasticallydeform the hollow cylindrical part 14 of the sealing plate 3 radiallyoutwardly, so that the narrow gap 30 is closed and an efficient seal isobtained between the billet container bore 15 and sealing plate 3. Thelarger gap 31 should be as large as is possible without running the riskof the billet material entering it.

We claim:
 1. An extrusion press for indirect extrusion comprisingacounter platen a cylinder cross-head tie-rods connecting the counterplaten and cylinder cross-head a moving cross-head a ram mounted on thecylinder cross-head for moving the moving cross-head a hollow stemmounted on the counter platen and extending towards the movingcross-head an extrusion die at the end of the hollow stem a billetcontainer between the moving cross-head and the counter platen, whichhas a billet-receiving bore and which can be moved by the movingcross-head over the die and hollow stem to perform an extrusionoperation a sealing plate for sealing one end of the said bore a hollowcylindrical portion provided on the sealing plate for projecting intosaid bore, and defining a cylindrical recess with an aperture at thebottom thereof a dummy block to be received in said cylindrical recess,.Iadd.said recess being sufficiently large to receive, in addition tothe dummy block, a portion of an extrusion butt-end formed in theextrusion process, .Iaddend.and a piston arranged in said aperture, andactuable to push the dummy block out of the recess. .[.2. The extrusionpress as claimed in claim 1, wherein said recess is sufficiently largeto receive, in addition to the dummy block, a portion of an extrusionbutt-end formed in the extrusion process..].
 3. The extrusion press asclaimed in claim 1, wherein the dummy block has a raised boss on itsfront face.
 4. An extrusion press for indirect extrusion comprisingacounter platen a cylinder cross-head tie-rods connecting the counterplaten and cylinder cross-head a moving cross-head a ram mounted on thecylinder cross-head for moving the moving cross-head a hollow stemmounted on the counter platen and extending towards the movingcross-head an extrusion die at the end of the hollow stem a billetcontainer between the moving cross-head and the counter platen, whichhas a billet-receiving bore and which can be moved by the movingcross-head over the die and hollow stem to perform an extrusionoperation a sealing plate for sealing one end of the said bore a hollowcylindrical portion provided on the sealing plate for projecting intosaid bore, and defining a cylindrical recess with an aperture at thebottom thereof a dummy block .[.filling.]. .Iadd.received in.Iaddend.said recess.Iadd., said recess being sufficiently large toreceive, in addition to the dummy block, a portion of an extrusionbutt-end formed in the extrusion process .Iaddend. a piston arranged insaid aperture, and actuable to push the dummy block out of the saidrecess, and wherein a first gap defined between the outer surface of thesealing plate and the billet container bore is made as small aspossible, and a second gap defined between the outer surface of thedummy block and the inner surface of the said recess is made as large aspossible .Iadd.without running the risk of billet material enteringit.Iaddend., so that the said second gap is pressurised during extrusionto elastically deform the hollow cylindrical portion into sealingcontact with the container bore. An extrusion press for indirectextrusion comprising:a counter platen, a cylinder cross-head, tie-rodsconnecting the counter platen and the cylinder cross-head, a movingcross-head, a ram mounted on the cylinder cross-head for moving themoving cross-head, a hollow stem mounted on the counter platen andextending towards the moving cross-head, an extrusion die at the end ofthe hollow stem, a billet container between the moving cross-head andthe counter platen, which has a billet receiving bore with a steppedportion at the moving cross-head end, the billet container being movableby the moving cross-head over the die and hollow stem to perform anextrusion operation, a sealing plate for sealing one end of said bore, ahollow cylindrical portion provided on the sealing plate for projectinginto said stepped portion of said billet receiving bore and defining acylindrical recess having a diameter equal to that of said billetreceiving bore and having an aperture at the bottom thereof, a dummyblock to be received in said cylindrical recess, .Iadd.said recess beingsufficiently large to receive, in addition to the dummy block, a portionof an extrusion butt-end formed in the extrusion process, and .Iaddend.a piston arranged in said aperture, and actuable to push the dummy blockout of the recess.